In a gas turbine or a turbo freezing machine, an axial-flow compressor, which is one type of axial-flow fluid machinery, is used to compress a gas. This type of axial-flow fluid machine sometimes includes a plurality of variable vanes disposed around a rotor in an annular shape, and a variable vane drive device configured to change directions of the variable vanes.
As disclosed in the following Patent Document 1 for example, the variable vane drive device includes a movable ring, a ring support mechanism, and an actuator. The movable ring is disposed at the outer circumferential side of a casing and has an annular shape. The ring support mechanism rotatably supports the movable ring. The actuator rotates the movable ring. The ring support mechanism has two first rollers and one second roller. The first rollers are disposed on the downside of the casing and an outer circumferential side of the movable ring at an interval in a circumferential direction of the movable ring. The second roller is disposed on the downside of the casing and an inner circumferential side of the movable ring at an interval from the two first rollers in the circumferential direction of the movable ring.